x/build/gerrit: add support for querying accounts in Gerrit

Added support for querying accounts in Gerrit. This is a pre-requisite
for golang/go#21216

Change-Id: Ic6776ddf18a23e347d0eb7edf91a934d2feb01c9
Reviewed-on: https://go-review.googlesource.com/61970
Reviewed-by: Kevin Burke <kev@inburke.com>

gerrit/gerrit.go

@@ -210,11 +210,19 @@ type ChangeInfo struct {
 	MoreChanges bool `json:"_more_changes"`
 }
 
+// AccountInfo is a Gerrit data structure. It's used both for getting the details
+// for a single account, as well as for querying multiple accounts.
 type AccountInfo struct {
 	NumericID int64  `json:"_account_id"`
 	Name      string `json:"name,omitempty"`
 	Email     string `json:"email,omitempty"`
 	Username  string `json:"username,omitempty"`
+
+	// MoreAccounts is set on the last account from QueryAccounts if
+	// the result set is truncated by an 'n' parameter (or has more).
+	MoreAccounts bool `json:"_more_accounts"`
+
+	// TODO: "avatars" is also returned, but not added here yet (add if required)
 }
 
 func (ai *AccountInfo) Equal(v *AccountInfo) bool {
@@ -550,6 +558,47 @@ func (c *Client) GetAccountInfo(ctx context.Context, accountID string) (AccountI
 	return res, err
 }
 
+// QueryAccountsOpt are options for QueryAccounts.
+type QueryAccountsOpt struct {
+	// N is the number of results to return.
+	// If 0, the 'n' parameter is not sent to Gerrit.
+	N int
+
+	// Start is the number of results to skip (useful in pagination).
+	// To figure out if there are more results, the last AccountInfo struct
+	// in the last call to QueryAccounts will have the field MoreAccounts=true.
+	// If 0, the 'S' parameter is not sent to Gerrit.
+	Start int
+
+	// Fields are optional fields to also return.
+	// Example strings include "DETAILS", "ALL_EMAILS".
+	// By default, only the account IDs are returned.
+	// For a complete list, see:
+	// https://gerrit-review.googlesource.com/Documentation/rest-api-accounts.html#query-account
+	Fields []string
+}
+
+// QueryAccounts queries accounts. The q parameter is a Gerrit search query.
+// For the API call and query syntax, see https://gerrit-review.googlesource.com/Documentation/rest-api-accounts.html#query-account
+func (c *Client) QueryAccounts(ctx context.Context, q string, opts ...QueryAccountsOpt) ([]*AccountInfo, error) {
+	var opt QueryAccountsOpt
+	switch len(opts) {
+	case 0:
+	case 1:
+		opt = opts[0]
+	default:
+		return nil, errors.New("only 1 option struct supported")
+	}
+	var changes []*AccountInfo
+	err := c.do(ctx, &changes, "GET", "/accounts/", urlValues{
+		"q": {q},
+		"n": condInt(opt.N),
+		"o": opt.Fields,
+		"S": condInt(opt.Start),
+	})
+	return changes, err
+}
+
 // GetProjects returns a map of all projects on the Gerrit server.
 func (c *Client) GetProjects(ctx context.Context, branch string) (map[string]*ProjectInfo, error) {
 	mp := make(map[string]*ProjectInfo)

gerrit/gerrit_test.go

@@ -178,6 +178,64 @@ func TestGetChangeError(t *testing.T) {
 	}
 }
 
+var queryAccountsResponse = []byte(`)]}'
+[
+  {
+    "_account_id": 1,
+    "name": "John Doe",
+    "email": "john@doe.com"
+  },
+  {
+    "_account_id": 2,
+    "name": "Jane Doe",
+    "email": "jane@doe.com",
+    "_more_accounts": true
+  }
+]`)
+
+func TestQueryAccounts(t *testing.T) {
+	hitServer := false
+	uri := ""
+
+	s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		hitServer = true
+		uri = r.URL.RequestURI()
+		w.Header().Set("Content-Type", "application/json; charset=UTF-8")
+		w.WriteHeader(200)
+		w.Write(queryAccountsResponse)
+	}))
+	defer s.Close()
+	c := NewClient(s.URL, NoAuth)
+	info, err := c.QueryAccounts(context.Background(), "is:active", QueryAccountsOpt{
+		Fields: []string{"DETAILS"},
+		N:      2,
+	})
+	if err != nil {
+		t.Fatal(err.Error())
+	}
+	if !hitServer {
+		t.Errorf("expected to hit test server, didn't")
+	}
+	if want := "/accounts/?n=2&o=DETAILS&q=is%3Aactive"; uri != want {
+		t.Errorf("expected RequestURI to be %q, got %q", want, uri)
+	}
+	if len(info) != 2 {
+		t.Errorf("expected accounts length to be 2, got %d", len(info))
+	}
+	if info[0].NumericID != 1 || info[0].Name != "John Doe" || info[0].Email != "john@doe.com" {
+		t.Errorf("expected to match John Doe in account, got %s", info[0])
+	}
+	if info[1].NumericID != 2 || info[1].Name != "Jane Doe" || info[1].Email != "jane@doe.com" {
+		t.Errorf("expected to match Jane Doe in account, got %s", info[1])
+	}
+	if info[0].MoreAccounts {
+		t.Errorf("expected to MoreAccounts to be false for John Doe")
+	}
+	if !info[1].MoreAccounts {
+		t.Errorf("expected to MoreAccounts to be true for Jane Doe")
+	}
+}
+
 func TestTimeStampMarshalJson(t *testing.T) {
 	ts := TimeStamp(time.Date(1888, 6, 24, 6, 8, 30, 123456789, time.FixedZone("+1", 3600)))
 	b, err := ts.MarshalJSON()